Near-infrared spectroscopic analysis of hemodynamics and mitochondrial redox in right lobe grafts in living-donor liver transplantation

Four Separate Hepatic Vein Reconstructions in Living-Donor Right-Lobe Liver Transplantation: Case Report

Living-donor liver transplantation (LDLT) with the use of a partial liver graft was established as an option to overcome the donor pool shortage, especially in developing countries. When right-lobe grafts are used for LDLT, appropriate venous drainage of the anterior segment is critical for maximizing the graft capacity. Here, we report a successful LDLT case using a right-lobe graft with 4 hepatic veins that were anastomosed separately to obtain adequate blood flow through the vena cava.

Microvascular tissue oxygenation and oxidative metabolism changes in the pedicled latissimus dorsi muscle during graded hypoxia: correlation between near infrared and 31P nuclear magnetic resonance spectroscopy

BACKGROUND

In this study, the microvascular tissue oxygenation and oxidative muscle metabolism during graded hypoxia and reoxygenation were examined in a rabbit model by near-infrared (NIR) spectroscopy and correlated with high-energy phosphates measured by (31)P nuclear magnetic resonance (NMR) spectroscopy.

MATERIALS AND METHODS

Graded hypoxia was performed in a New Zealand rabbit model (n = 20, 2.0 ± 0.4 kg) by a stepwise reduction of the fraction of inspired oxygen (FiO(2)) from 0.3 to 0.05 (intervention group versus control group). Recovery and reoxygenation were achieved using FiO(2) of 0.3. A noninvasive NIR spectroscopy sensor and NMR probe was positioned on the surface of the prepared pedicled latissimus dorsi muscle. Microvascular tissue oxygenation (oxyhemoglobin, HbO(2); deoxyhemoglobin, HHb) and redox state of cytochrome oxidase (CytOx) were measured by NIR spectroscopy and correlated with standard values of oxidative muscle metabolism (phosphocreatine, PCr; adenosine triphosphate, ATP) measured by time-resolved (31)P NMR spectroscopy (4.7T).

RESULTS

Significant correlation was found between PCr and HbO(2) (r = 0.85, P < 0.001) and HHb (r = -0.75, P < 0.001). β-ATP levels correlated significantly with CytOx (r = 0.87, P < 0.001).

CONCLUSIONS

The data suggest that changes in high-energy phosphates (PCr- and ATP-levels) correlate closely with microvascular tissue oxygenation (HbO(2), HHb, CytOx) measured by NIR spectroscopy.

In vivo characterization of myocardial infarction using fluorescence and diffuse reflectance spectroscopy

We explore the feasibility of using combined fluorescence and diffuse reflectance spectroscopy to characterize a myocardial infarct at different developing stages. An animal study is conducted using rats with surgically induced myocaridal infarction (MI). In vivo fluorescence spectra at 337-nm excitation and diffuse reflectance between 400 and 900 nm are measured from the heart. Spectral acquisition is performed: 1. for normal heart tissue; 2. for the area immediately surrounding the infarct; and 3. for the infarcted tissue itself, one, two, three, and four weeks into MI development. Histological and statistical analyses are used to identify unique pathohistological features and spectral alterations associated with the investigated regions. The main alterations (p<0.05) in diffuse reflectance spectra are identified primarily between 450 and 600 nm. The dominant fluorescence alterations are increases in peak fluorescence intensity at 400 and 460 nm. The extent of these spectral alterations is related to the duration of the infarction. The findings of this study support the concept that optical spectroscopy could be useful as a tool to noninvasively determine the in vivo pathophysiological features of a myocardial infarct and its surrounding tissue, thereby providing real-time feedback to surgeons during various surgical interventions for MI.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Sinusoidal perfusion in the veno-occlusive region of living liver donors evaluated by indocyanine green and near-infrared spectroscopy

Split liver transplantation and living donor liver transplantation (LDLT) commonly use a right liver graft without the middle hepatic vein (MHV). Although tributaries of the MHV are not reconstructed in the majority of cases, the alterations of the microcirculation and its regional functions remain unknown. We addressed these issues by assessing liver tissue indocyanine green (ICG) uptake with near-infrared spectroscopy (NIRS) in 21 donors. After graft procurement, visual inspection (before and after hepatic arterial clamping) and Doppler examination of the veno-occlusive region were performed. Bolus ICG (100 microg/kg) was then administered intravenously. Blood ICG at the finger tip was measured with pulse dye densitometry, whereas the liver ICG concentrations in the veno-occlusive and non-veno-occlusive regions were simultaneously measured for 15 minutes by NIRS. We estimated the hepatic ICG uptake rate constants in the veno-occlusive region (Ku-oc) and non-veno-occlusive region (Ku-non). Changes in sinusoidal perfusion in the veno-occlusive region were expressed by the ratio of Ku-oc to Ku-non (Roc/non). The median value of Roc/non was 0.47, although it ranged from 0.13 to 0.94. Roc/non was related to the extent of liver surface discoloration before and after hepatic arterial clamping (P = 0.03 and 0.01, respectively). In conclusion, sinusoidal perfusion was impaired in the veno-occlusive regions of living donor livers, but the magnitude of the effect varied greatly. Measurement of hepatic ICG uptake by NIRS could become a valuable tool for assessing the indication for venous reconstruction in LDLT and/or split donor liver transplantation.

Near Infrared Spectroscopy (NIRS) in Children

Near infrared spectroscopy (NIRS) is a noninvasive method for the in vivo monitoring of tissue oxygenation. Originally used predominantly to assess cerebral oxygenation, NIRS has gained widespread popularity in many clinical settings in all age groups. Changes in regional tissue oxygenation as detected by NIRS may reflect the delicate balance between oxygen delivery and consumption in more than one organ system. However, more studies are required to establish the ability of NIRS monitoring to improve patient outcome. This review provides a comprehensive description of NIRS in children.